The invention is directed to a device for and a method of removing carious tooth material by laser light emitted from a pulsed laser light source.
From DE 38 00 555 A, the use of ultraviolet laser light with a wavelength of 193 nm is known, which is emitted from an argon fluoride excimer laser. The photon energy of the laser light is cumulated to magnitudes that are greater than the binding energies of the respective hard tooth substances to be dissolved. With an energy density of at least 5000 mJ/mm.sup.2 per pulse and focussing on a light spot of about 1-2 mm.sup.2, it is said to be possible to generate a pulse energy density at which the threshold value to the beginning of photodecomposition is exceeded by a sufficient extent. For the repetition reate, it is suggested to select a frequency of less than 100 Hz. The laser pulse period is about 15 to 20 ns. This known method is to allow for a controlled removal of unaffected or carious hard tooth substances. From U.S. Pat. Nos. 4,521,194 and 4,818,230, it is known to use an yttrium aluminium garnet laser (wavelength 1064 nm), the output energy of which is within the range of 1 to 100 mJ at a pulse duration of several picoseconds to several milliseconds, and the light beam diameter of which is in the range of 50 to 2000 .mu.m.
The known devices allow for a treatment of both carious dentine and non-carious softened dentine. Here, it is a drawback that, as in conventional drilling, unaffected hard tooth substance is removed when removing carious dentine or carious tooth material, thus leading to an unnecessary reduction of the hard tooth substance.
It is a further drawback of known prior art that a high energy density is introduced so that the thermal stress on the tooth may also cause damages to adjacent areas.
A further problem arises with laser devices that require a focussing of the laser beam: with these devices, an exact observation of a defined distance is necessary in order to keep the light spot diameter, and thus the energy density introduced, constant. To accomplish this, complex devices are required that also hinder a dentist's work.
From the posteriorly published EP 0 375 578 A, a Nd:YAG laser with a wavelength of 532 nm is known to be used for dental treatment. The output energy of the laser per pulse is 10 to 50 mJ at a frequency of 50 Hz. The pulse duration is between 100 and 300 .mu.s. The laser beam is focussed onto a light spot diameter between 0.2 and 0.6 mm via a converging mirror.